Code completion for overloaded methods

ABSTRACT

A code completion tool uses machine learning models to more precisely predict the likelihood of an invocation of a particular overloaded method completing a code fragment that follows one or more method invocations of a same class in a same document during program development. In one aspect, the machine learning model is a n-order Markov chain model that is trained on features that represent the method signatures of overloaded methods in order to generate ordered sequences of method signatures of overloaded method invocations.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patent application Ser. No. 15/939,742, filed on Mar. 29, 2018 which claims the benefit of provisional application having Ser. No. 62/619,806 filed on Jan. 21, 2018. The present application claims the benefit of provisional application having Ser. No. 62/664,191 filed on Apr. 29, 2018 and hereby incorporates subject matter of the provisional application in its entirety.

BACKGROUND

Software development environments are often used to aid software developers (i.e., users, programmers, etc.) to develop program code. The software development environment may include a source code editor and other tools that the developers utilize to write and test their programs. Some software development environments provide assistance for the developer to write code by automatically presenting a list of possible candidates based on one or more characters (e.g., letters, symbols, etc.) that a developer has typed into a source code editor. A popup menu may appear with several suggested code elements, phrases, or entities that the developer may utilize. This assistance is beneficial since it speeds up the development time and reduces common errors, such as typos. However, the automatic code completion feature may be problematic when there is a large list of candidates which may not be relevant and/or which may be too lengthy for a developer to browse through to find the right element.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

A code completion tool utilizes sequential machine learning models to predict more accurately those methods more likely to complete a method invocation. The machine learning models are trained on usage patterns found in commonly-used source code programs. The usage patterns are detected from the characteristics of the context in which a method invocation is used in a program. These characteristics are extracted from data structures representing the syntactic structure and semantic model representations of a program. A machine learning model is generated for each class and contains ordered sequences of method invocations with probabilities representing the likelihood of a transition from a particular method invocation sequence to a succeeding method invocation. In one aspect, the machine learning model is an n-order Markov chain model which is used to predict what method will be used in a current invocation based on preceding method invocations of the same class in the same document and the context in which the current method invocation is made.

In a second aspect, the machine learning model considers overloaded methods of a class that have the same method name but different method signatures. The machine learning model is generated for each class based on an ordered sequence of method signatures with probabilities representing the likelihood of a transition from a particular method invocation having a particular method signature to an immediately succeeding method invocation having a same or different method signature.

During code development, an autocompletion component of a source code editor uses the sequential machine learning models to generate candidates to complete a method invocation. The machine learning model uses one or more immediately preceding method invocations and the characteristics of the context of the current position to predict the more likely methods to complete a method invocation.

In a second aspect, the machine learning model uses the method signatures of the immediately preceding method invocations of a class and the characteristics of the context of the current position in order to predict the more likely method and its corresponding method signature to complete a method invocation. The machine learning model is embodied as a n-order Markov chain model. The n-order Markov model includes one or more ordered sequences of method signatures that were used in method invocations. A sequence includes transition probabilities representing a likelihood of transitioning from one method invocation having a first method signature to another method invocation having a second method signature. In this manner, the code completion system is able to predict the method signature of an overloaded method invocation instead of predicting just the method name.

These and other features and advantages will be apparent from a reading of the following detailed description and a review of the associated drawings. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of aspects as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an exemplary system including a training phase used to generate machine learning models for code completion and an execution phase that uses the machine learning models for code completion.

FIG. 2A is a schematic diagram illustrating the extraction of features from a source code program.

FIG. 2B illustrates an exemplary second-order Markov model embodied in a lookup table or dictionary format.

FIG. 3 is a flow diagram illustrating an exemplary method for generating the machine learning models.

FIG. 4 is a flow diagram illustrating an exemplary method for utilizing the machine models for code completion.

FIGS. 5A-5B illustrate exemplary pop-up windows including code completion candidates.

FIG. 6 is a block diagram illustrating an operating environment.

FIG. 7A is a schematic diagram illustrating the features extracted from a source code program in a second aspect of the disclosure.

FIG. 7B illustrates an exemplary second-order Markov model embodied in a lookup table or dictionary format.

FIG. 8 is a flow diagram illustrating an exemplary method for generating method-signature based machine learning models.

FIG. 9 is a flow diagram illustrating an exemplary method for utilizing the method-signature based machine learning models in a code completion system.

FIG. 10 illustrates an exemplary user interface providing candidates for completing a method invocation using the method-signature based machine learning models.

DETAILED DESCRIPTION

Overview

The subject matter disclosed pertains to a mechanism for generating candidates for code completion or autocompletion of a method invocation. A method invocation is the issuance of a call to a method or property of a class. A class may include a large number of methods and/or properties thereby making it impractical to list all the methods and properties of a class as candidates. In order to generate candidates more likely to complete a source code statement invoking a method, the context in which the method is invoked is used to predict the more likely candidates.

Method invocations differ with respect to the context in which they are used in a program. The context of a method invocation may include one or more of the following: the spatial position of the method call in the program; whether the method call is inside a conditional branch (e.g., if-then-else program construct); the name of the class; the name of the method or property invoked; the name of the class corresponding to the invoked method; the function containing the method invocation; the type of the method; and an indication if the method is associated with an override, static, virtual, definition, abstract, and/or sealed keyword. This context information is collected from various programs and used to detect sequential patterns in the method invocations of a class. The context information is used as the features that train a machine learning model to predict the next method to complete a method invocation.

In one aspect, an n-order Markov chain model is generated based on the context information extracted from method invocations found in various programs written in a specific programming language. Markov chain models are used in code completion to predict what method will be used in a current invocation based on preceding method invocations of the same class in the same document and the context in which the current method invocation is made.

Method overloading is a feature that allows a class to have more than one method with the same name but with different parameter lists. The number, type and order of the parameters differs for each overloaded method with the same method name. In another aspect, an n-order Markov chain model is generated based on the context information extracted from overloaded method invocations and non-overloaded method invocations found in various programs written in a specific programming language. The n-order Markov chain models are used in code completion to predict what method signature will be used in a current method invocation based on the preceding method signatures used in method invocations of the same class and the context in which the current method invocation is made.

Attention now turns to a further discussion of the system, devices, components, and methods utilized in a code completion system.

Machine Learning Code Completion System

FIG. 1 illustrates a block diagram of an exemplary system 100 in which various aspects of the invention may be practiced. As shown in FIG. 1, system 100 includes a training phase 102 which generates a model for each class and an execution phase 104 that utilizes the class models in a code completion system. The training phase 102 may utilize a source code extraction component 108, a compilation component 112, a feature extraction component 116, a model generation component 122 and a model test component 126. The execution phase 104 may utilize a source code editor 130, an auto completion component 136, and a dictionary 138.

In the training phase 102, the source code extraction component 108 extracts source code programs 110 from a source code repository 106 to train the machine learning models. A compilation component 112 compiles the selected source code programs 110 to generate a corresponding syntax tree and semantic model 114. In one aspect, the compilation component 112 may be a front-end compiler, a parser, or a language compiler.

A syntax tree or abstract syntax tree represents the syntactic structure of the program in a hierarchical or tree structure. The syntax tree is a data structure that includes nodes that represent a construct in the grammar of the programming language of the program. The semantic model includes all the semantic information about the program. The semantic model includes information on the symbols referenced at a specific location in the program. Every namespace, type, method, property, field, event, parameter, label, and local variable maybe represented by a symbol. Symbols may also include additional information that a compiler determines from the program, such as methods and properties associated with the symbol. The semantic model encapsulates all this data into a data structure referred to as the semantic model.

The syntax tree and the semantic model 114 of each selected source code program is passed to the feature extraction component 116. The feature extraction component 116 extracts certain features of a method invocation from the syntax tree and semantic model. A feature is a discriminable characteristic of the method invocation that represents the context in which a method is called. There are several features extracted for each method invocation and these features comprise a feature vector. A portion of the feature vectors generated for a particular class can then be used as training data for the model generation component 112 to train a model 118. Another portion of the feature vectors 120 can be used by the model test component 126 to test the model 120.

In one aspect, the features may include one or more of the following: the position of a method invocation within the program (e.g., span start); whether the method invocation is within a conditional branch (e.g., if-then-else statement, switch or case statement); the class name corresponding to the method invocation, the name of the method or property invoked; the name of the class that contains the called method; the function that contains the called method; the type of the method; and an indication of whether the called method is associated with the static, virtual, override, definition, abstract and/or sealed keywords.

The models 128 may then be used in code completion. The execution phase 104 may include a source code editor 130 having a user interface 132 and a parser 134, an auto completion component 136, and one or more dictionaries 138. In one or more aspects, code completion may be a function or feature integrated into a source code editor and/or integrated development environment (IDE). Code completion may be embodied as a tool or feature that can be an add-on, plug-in, extension and/or component of a source code editor and/or IDE.

In one aspect, a source code editor 130 may include a user interface 132 and a parser 134. The user interface 132 includes a set of features or functions for writing and editing a source code program. The user interface 132 may utilize a pop-up window to present a list of possible candidates for completion thereby allowing a developer to browse through the candidates and to select one from the list. In this manner, code completion serves as documentation for the method invocations associated with a class in addition to being an assistance to writing code quickly. The parser 134 reads the source code in the source code editor 130 and generates a corresponding syntax tree and semantic model 140. The parser 134 also updates the syntax tree and semantic model 140 as the developer creates and edits the source code in the source code editor 130.

At certain points in the editing process, the user interface 132 will detect that the user has entered a particular character which will initiate code completion. In one aspect, the character that initiates code completion may be a period, “.”, placed after a class name. The user interface 132 will then request candidates from the auto completion component 136 to present to the developer.

The auto completion component 136 receives requests 144 for candidates to complete a method invocation. The auto completion component 136 extracts the previous method invocations for the same class in the same document used in the current invocation and the context of the current invocation by accessing the syntax tree and semantic model representation of the source code program in the source code editor.

The auto completion component 136 utilizes one or more dictionaries 138 which contain the models 128 in a lookup table format. There is one model for each class. A dictionary 138 corresponding to the class name is accessed based on a sequence of method invocations. The corresponding entry has a list of methods ranked by their predicted probabilities. The auto completion component 136 obtains one or more candidates 142 from the dictionary 138 which are returned back to the user interface 132. In one aspect, at most five candidates are obtained from the dictionary 138. The user interface 132 in turn provides the candidates to the developer. In one aspect, the user interface 132 may provide the candidates from the auto completion component with other candidates from other code completion tools and/or provide the candidates from the machine learning based auto completion component separately. The techniques describe herein are not constrained to any particular mechanism for providing the candidates to a developer and the manner in which the candidates are displayed to the user (e.g., pop-up window, etc.).

It should be noted that FIG. 1 shows components of the system in one aspect of an environment in which various aspects of the invention may be practiced. However, the exact configuration of the components shown in FIG. 1 may not be required to practice the various aspects and variations in the configuration shown in FIG. 1 and the type of components may be made without departing from the spirit or scope of the invention. For example, the training phase 102 may be executed in one computing environment and the execution phase 104 may be executed in the same computing environment or in a separate computing environment. The various computing environment is described in further detail below.

FIG. 2A illustrates the extraction of the features used to train a Markov chain model. Source code program 202 contains at line 17 an invocation of the method Console.Writeline( ). The Console.Writeline method is part of the System.Console class. The features that are extracted from this method invocation are placed into feature vector 204. Feature vector 204 includes the following features: span start=9 (206); if conditional=false (208); class name=System.Console (210); the name of the method=Writeline (212); the name of the class containing the method=Program (214); the name of the function containing the method invocation=Main (216); the type of the method=Named Type (218); and if the method is associated with the keywords override, static, virtual, definition, abstract, and sealed=False (220).

Feature vector 204 as well as other feature vectors associated with method invocations of the System.Console class are used to train a model to predict the most likely candidates to complete the method invocation. The model is a sequential or chain model that is capable of modeling sequences of events. In one aspect, the model is a Markov chain model. A Markov chain model relies on the assumption that each state is dependent on previous states. The dependency is given by a conditional probability P(x_(t)|x_(t-1), . . . , x_(t-N)), where x_(t) is the state of the model at time t and n is the order of the Markov chain. In a first order Markov chain, a state is dependent only on the immediately preceding state and in a second order Markov chain model, a state is dependent on the immediately preceding two states.

The transition probabilities are generated from the sequential usage patterns detected in the training data. In one aspect, the probabilities may be computed as P(x_(t)|x_(t-1), . . . x_(t-n))=N_(t)/N_(total), where n is the order of the Markov chain, N_(t) is the number of times x_(t) comes after x_(t-1) and x_(t-2), N_(total)=total number of methods that come after x_(t-1) and x_(t-2). Each model represents a particular class and contains sequences of method invocations that result in an end state that represents a method invocation within the class.

FIG. 2B illustrates an exemplary second order Markov chain model embodied as a lookup table (i.e., dictionary, key-value pair). In one aspect, there are at least two lookup tables for each class 222A,222B. One lookup table is for method invocations outside of a conditional branch 222A and the other lookup table is for method invocations within a conditional branch 222B. The key into either table is a method invocation sequence of two previous method invocations in the System.Console class. The corresponding entry in the table is a list of methods in the System.Console class ranked in order of highest probability for completing a current invocation.

As shown in FIG. 2B, when the sequence of preceding method invocations of the System.Console class are Method A followed by Method Y 224, the key into the table is the sequence Method A, Method Y. The corresponding entry in the table 222A lists the code completion candidates as Method B, Method Z, Method S, ordered in highest probability to lowest probability. Likewise, when the preceding method invocations of the System.Console class are Method J followed by Method A 226, the code completion candidates are Method S, Method U, and Method D. When there is only one preceding method invocation for a class in a document, a null value is used to represent the missing method invocation and the key is the method sequence NULL, Method X. The corresponding entry is Method E.

When the current invocation is inside a conditional branch (i.e., if-then-else statement), then the System. Console class conditional branch table 222B is used. The previous sequence of method invocations for the System.Console class in the same document is used as the key into this table. When the preceding sequence of method invocations is Method A followed by Method Y 224, then the code completion candidates are Method NN and Method LN, where Method NN has a higher probability then Method LN. Likewise, when the preceding sequence of method invocations is Method J followed by Method A 226, the code completion candidate is Method ST. When there is only one preceding method invocation, the key is the sequence NULL, Method X 228 and the candidate is Method PL.

Attention now turns to description of the various exemplary methods that utilize the system and device disclosed herein. Operations for the aspects may be further described with reference to various exemplary methods. It may be appreciated that the representative methods do not necessarily have to be executed in the order presented, or in any particular order, unless otherwise indicated. Moreover, various activities described with respect to the methods can be executed in serial or parallel fashion, or any combination of serial and parallel operations. In one or more aspects, the method illustrates operations for the systems and devices disclosed herein.

FIG. 3 illustrates an exemplary method illustrating the generation of the machine learning models for code completion. Referring to FIGS. 1 and 3, one or more source code repositories 106 are searched for source code programs written in a target programming language. The source code repositories 106 can be widely-used code repositories, such as GitHub, internal code repositories, and/or combinations thereof. The source code extraction component 108 extracts a number and type of source code programs that meet an intended target, such as source code programs that are accessed frequently, source code programs that utilize a particular function (e.g., database operations, computer graphics programs, etc.), and the like (collectively, block 302).

The selected source code programs 110 are then compiled by the compilation component 112 to produce data structures representing the syntax tree and semantic model of the source code (block 304). The syntax tree and semantic model 114 are used by the feature extraction component 116 to extract characteristics representative of the context of a method invocation. These characteristics are used to determine the order in which methods are invoked in a program having conditional branches (block 306). The characteristics include one or more of the following: the position of a method invocation within the program (e.g., span start); whether the method invocation is within a conditional branch (e.g., if-then-else statement, switch or case statement); the class name corresponding to the method invocation, the name of the method or property invoked; the name of the class that contains the called method; the function that contains the called method; the type of the method; and an indication of whether the called method is associated with the static, virtual, override, definition, abstract and/or sealed keywords.

The characteristics are configured into feature vectors which serve as the training and testing data for the models. In one aspect, the feature vector can be split with 80% used as training data and 20% used as testing data (collectively, block 306).

The feature vectors in the training data are used by the model generation component to generate the models. The data in the feature vectors is used to determine an order of the method invocations in each program for each class. From the ordered list of method invocations, sequences of usage patterns can be detected. These patterns can then be partitioned into sequences having n+1 states, where n is the order of the Markov chain model. These sequences are then used to train a Markov chain model for each class which entails generating the states and transition probabilities (collectively, block 308).

The training data is analyzed to detect sequences of method invocations for each class. For an n-order Markov chain model, the number of specific n state method invocation sequences that occur is counted to order the n+1 states that occur thereafter by derived probabilities. The derived probability may be generated by the ratio of the number of times the n+1 state sequence occurs over the number of times the n state sequence occurs (block 308).

The models are then tested to ensure a target level of accuracy (block 310). The testing entails providing each model with test data and checking the recommendations that the model outputs. When the recommendations achieve a certain level of accuracy, then the models are transformed into a dictionary or lookup table format and released (block 312).

FIG. 4 illustrates an exemplary method of code completion utilizing the machine learning models. Referring to FIGS. 1 and 4, code completion is performed in a development environment such as a source code editor 130. The source code editor 130 is configured to interact with an auto completion component 136 that utilizes the machine learning models in a lookup table format (block 402). The source code editor 130 performs a background parsing process that parses the source code in the source code editor to generate and update the syntax tree and semantic model of the source code (block 402).

The user interface 132 of the source code editor 130 detects the input characters that a developer enters into the source code editor 130. When the user interface 132 detects a particular character that denotes code completion is needed for a method invocation at a current position in the source code editor 130, the user interface 132 requests recommendations 144 from the auto completion component 136 (block 404). In one aspect, the detection of a period after a class name is used as the trigger to invoke code completion (block 404).

The auto completion component 138 utilizes the syntax tree and semantic model 140 generated during the source code editing session to obtain the previous method invocations that have occurred before the current position in the source code editor 130 and the characteristics of the context of the current method invocation, such as whether the current method invocation is inside a conditional branch (block 406). In one aspect, application program interfaces (APIs) may be used to extract the previous method invocations from the syntax tree and semantic model and the characteristics of the context of the current position (block 406).

The auto completion component 136 utilizes the dictionary 138 associated with the class to search for a sequence most likely to predict the next method invocation using the characteristics of the context of the current position (block 408). Once the auto completion component 136 obtains the previous method invocations, an n-state sequence can be constructed and used as a key to access the dictionary. The corresponding values are used as the recommendations. If there is no such n-state sequence, then the dictionary is searched using an n−1 state sequence constructed from the previous n−1 method invocations in the same class. If the n−1 state sequence cannot be found in the dictionary, then the n−2 state sequence is used to search the dictionary. In an n-order Markov chain model, the n−1 state sequence will be stored as a new n state sequence with the first state marked as null.

The auto completion component 136 may find one or more candidates for recommendation from the sequences in the dictionary (block 408). In the event that there are multiple candidates, the auto completion component 136 orders the recommendations by highest probability (block 410). The candidates are then returned to the user interface for display to the developer (block 412).

FIGS. 5A-5B illustrate exemplary user interfaces. FIG. 5A shows an exemplary source code program 502 in a source code editor that display pop-up window 504 containing candidates for code completion. As shown in FIG. 5A, the suggested method to complete the expression !dir. is the method Exists. FIG. 5B shows an exemplary source code program 506 in a source code editor that displays pop-up window 508 containing multiple recommendations. The recommendation from the auto completion component may be distinguished with a star * and other recommendations are included thereafter in alphabetical order.

Technical Effect

Aspects of the subject matter disclosed herein pertain to the technical problem of providing more precise candidates for code completion. The technical feature associated with addressing this problem involves an n-order Markov chain model that predicts a method for completion of a method invocation. The Markov chain model is trained using sequences of usage patterns of historical method invocations from a sampled population of existing source code programs. Characteristics of the context in which a method is invoked is extracted from the sampled programs in order to recognize sequential patterns in the usage of a method invocation. These characteristics serve as the training data which trains the Markov chain model to more particularly predict a method to complete a method invocation. In this manner, the source code editor presents more relevant candidates for code completion.

Exemplary Operating Environment

Attention now turns to a discussion of an exemplary operating environment. FIG. 6 illustrates an exemplary operating environment 600 in which a first computing device 602 is used to train the machine learning models and a second computing device 604 uses the machine learning models for code completion. However, it should be noted that the aspects disclosed herein is not constrained to any particular configuration of devices. Computing device 602 may utilize the machine learning models in its own code completion system and computing device 604 may generate and test machine learning models as well. Computing device 602 may be configured as a cloud service that generates machine learning model as a service for other code completion systems. The operating environment is not limited to any particular configuration.

The computing devices 602, 604 may be any type of electronic device, such as, without limitation, a mobile device, a personal digital assistant, a mobile computing device, a smart phone, a cellular telephone, a handheld computer, a server, a server array or server farm, a web server, a network server, a blade server, an Internet server, a work station, a mini-computer, a mainframe computer, a supercomputer, a network appliance, a web appliance, a distributed computing system, multiprocessor systems, or combination thereof. The operating environment 600 may be configured in a network environment, a distributed environment, a multi-processor environment, or a stand-alone computing device having access to remote or local storage devices.

The computing devices 602, 604 may include one or more processors 608, 634, a communication interface 610, 636, one or more storage devices 612, 638, one or more input/output devices 614, 640, and a memory 616, 642. A processor 608, 634 may be any commercially available or customized processor and may include dual microprocessors and multi-processor architectures. The communication interface 610, 636 facilitates wired or wireless communications between the computing device 602, 604 and other devices. A storage device 612, 638 may be computer-readable medium that does not contain propagating signals, such as modulated data signals transmitted through a carrier wave. Examples of a storage device 612, 638 include without limitation RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage, all of which do not contain propagating signals, such as modulated data signals transmitted through a carrier wave. There may be multiple storage devices 612, 638 in the computing devices 602, 604. The input/output devices 614, 640 may include a keyboard, mouse, pen, voice input device, touch input device, display, speakers, printers, etc., and any combination thereof.

A memory 616, 642 may be any non-transitory computer-readable storage media that may store executable procedures, applications, and data. The computer-readable storage media does not pertain to propagated signals, such as modulated data signals transmitted through a carrier wave. It may be any type of non-transitory memory device (e.g., random access memory, read-only memory, etc.), magnetic storage, volatile storage, non-volatile storage, optical storage, DVD, CD, floppy disk drive, etc. that does not pertain to propagated signals, such as modulated data signals transmitted through a carrier wave. A memory 616, 642 may also include one or more external storage devices or remotely located storage devices that do not pertain to propagated signals, such as modulated data signals transmitted through a carrier wave.

Computing device 604 may utilize an integrated development environment (IDE) 620 that allows a user (e.g., developer, programmer, designer, coder, etc.) to design, code, compile, test, run, edit, debug or build a program, set of programs, web sites, web applications, and web services in a computer system. Software programs can include source code files 618, created in one or more source code languages (e.g., Visual Basic, Visual J#, C++. C#, J#, Java Script, APL, COBOL, Pascal, Eiffel, Haskell, ML, Oberon, Perl, Python, Scheme, Smalltalk and the like). The IDE 620 may provide a native code development environment or may provide a managed code development that runs on a virtual machine or may provide a combination thereof. The IDE 620 may provide a managed code development environment using the .NET framework. It should be noted that this operating embodiment is not constrained to providing the source code development services through an IDE and that other tools may be utilized instead, such as a stand-alone source code editor and the like.

A user can create and/or edit the source code files 618 according to known software programming techniques and the specific logical and syntactical rules associated with a particular source language via a user interface 624 and a source code editor 622 in the IDE 620. Thereafter, the source code files 618 can be compiled via a compiler 626, such as a front end or language compiler. During this compilation process, the front-end compiler 626 generates data structures representing the syntactic structure and semantic model of the source code.

The memory 642 may contain instructions, components, and data. A component is a software program that performs a specific function and is otherwise known as a module, program, and/or application. The memory 642 may include an operating system 616, one or more source code files 618, an IDE that may include a source code editor 622, a user interface 624, a compiler 626, an autocompletion component 628, dictionaries 630 and other applications and data 632. Memory 616 may include an operating system 642, a model test component 644, a feature extraction component 646, a model generation component 648, a compilation component 650, a source code extraction component 652, models/dictionaries 654, and other applications and data 656.

The computing devices 602, 604 may be communicatively coupled via a network 606. The network 634 may be configured as an ad hoc network, an intranet, an extranet, a virtual private network (VPN), a local area network (LAN), a wireless LAN (WLAN), a wide area network (WAN), a wireless WAN (WWAN), a metropolitan network (MAN), the Internet, a portions of the Public Switched Telephone Network (PSTN), plain old telephone service (POTS) network, a wireless network, a WiFi® network, or any other type of network or combination of networks.

The network 634 may employ a variety of wired and/or wireless communication protocols and/or technologies. Various generations of different communication protocols and/or technologies that may be employed by a network may include, without limitation, Global System for Mobile Communication (GSM), General Packet Radio Services (GPRS), Enhanced Data GSM Environment (EDGE), Code Division Multiple Access (CDMA), Wideband Code Division Multiple Access (W-CDMA), Code Division Multiple Access 2000, (CDMA-2000), High Speed Downlink Packet Access (HSDPA), Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), Evolution-Data Optimized (Ev-DO), Worldwide Interoperability for Microwave Access (WiMax), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiplexing (OFDM), Ultra Wide Band (UWB), Wireless Application Protocol (WAP), User Datagram Protocol (UDP), Transmission Control Protocol/Internet Protocol (TCP/IP), any portion of the Open Systems Interconnection (OSI) model protocols, Session Initiated Protocol/Real-Time Transport Protocol (SIP/RTP), Short Message Service (SMS), Multimedia Messaging Service (MMS), or any other communication protocols and/or technologies.

A system is disclosed that contains one or more processors, a memory and one or more programs, where the one or more programs are stored in memory. The one or more programs are configured to be executed by the one or more processors and have instructions for generating a data structure representing a syntactic structure and a semantic model of a program, extracting a plurality of features from the data structure to construct one or more feature vectors, the plurality of features including characteristics of a context of a method invocation found within a program, and training a sequential model for a first class from the one or more feature vectors to predict a next method invocation for code completion following one or more preceding method invocations of a same class as the first class, wherein the sequential model includes one or more sequences of method invocations with probabilities for transitioning between each method invocation in the one or more sequences.

The sequential model may be an n-order Markov chain model. The data structure includes a syntax tree and a semantic model and is generated from compilation of the program. The characteristics of a context of a method invocation includes one or more of a spatial position of a method invocation, a name of a class associated with a method invocation, a name of a method or property invoked, and a name of a function containing a method invocation. The characteristics of a context of a method invocation may also include whether a method invocation is included in a conditional branch and identifiers indicating whether a method invocation is associated with an override, static, virtual, definition, abstract, and/or sealed keyword.

A device is disclosed that includes at least one processor and a memory. The device is configured to extract one or more features from a plurality of source code programs where a source code program has one or more method calls. The features represent a context in which a method is called in the source code program and at least one feature represents a location of the called method in the program. The device is further configured to generate one or more sequences of method calls of length n from the extracted one or more features. A sequence includes method calls occurring in successive order. A sequence includes a probability from transitioning from one method in a sequence to an immediately succeeding method in the sequence, wherein the sequences and probabilities are computed from usage patterns of historical source code programs. The device is further configured to train sequences to predict a method to complete a method invocation in a program using a context of the method invocation and at least one immediately preceding method invocation.

A sequence of method calls of length n are represented as an n-order Markov chain model. The features may include a name of a class associated with a method invocation, a name of a method or property invoked, a name of a function containing a method invocation, an indication of whether a method invocation is included in a conditional branch, and identifiers indicating whether a method invocation is associated with an override, static, virtual, definition, abstract, and/or sealed keyword. The features are extracted from a syntax tree and/or semantic model representation of the plurality of source code programs. The syntax tree and semantic model representation of a source code program is generated from a compilation of a source code program.

A method is disclosed that can implemented on a system or device disclosed herein which obtains at least one method invocation in a source code program occurring immediately preceding a current position in a source code editor, determines a class associated with input at the current position, utilizes a Markov chain model to predict one or more recommendations of methods to complete a method invocation at the current position, and produces the one or more predicted recommendations of methods using the Markov chain model using the at least one previous method invocation in the source code program and characteristics of a context at the current position.

The Markov chain model includes one or more sequences of method invocations where a sequence includes transition probabilities representing a likelihood of transitioning from one method invocation to another method invocation in a sequence. The method generates a data structure that tracks a syntax structure and semantic model of the source code program in the source code editor and uses the data structure to obtain the at least one previous method invocation in a source code program occurring immediately preceding the current position. The method uses the data structure to obtain the characteristics of the context of the current position. The method ranks the one or more predicted code completion recommendations in order of highest probability.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Method Signature Based Code Completion

Referring to FIG. 1, in a second aspect, the training phase 102 and the components shown therein are used to generate a model for each class based on method signatures and the execution phase uses the method-signature-based models in a code completion system. The use of ordered sequences of method invocations represented by method signatures improves the prediction accuracy of the code completion system. The code completion system can differentiate between the different overloaded methods that have the same method name and provide a more accurate recommendation through the use of method signatures.

A method signature contains a method name, the number, type, and order of parameters. For example, the WriteLine method of the System.Console class in the C# programming language has nineteen different WriteLine methods with each WriteLine method using different parameters. These WriteLine methods are as follows:

WriteLine( ), WriteLine(Boolean), WriteLine(Char), WriteLine(Char[ ]), WriteLine(Char, Int32, Int32), WriteLine(Decimal), WriteLine(Double), WriteLine(Int32), WriteLine(Int64), WriteLine(Object), WriteLine(Single), WriteLine(String), WriteLine(String Object), WriteLine(String Object Object), WriteLine (String Object Object Object), WriteLine(String Object Object Object Object), WriteLine(String Object[ ]), WriteLine(String UInt32), WriteLine(UInt64). Instead of providing a method name, such as WriteLine, the method signature of the more likely WriteLine method is provided to the user.

In the training phase 102, the source code extraction component 108 extracts selected source code programs 110 from a source code repository 106 to train the machine learning models. A compilation component 112 compiles the selected source code programs 110 to generate a corresponding syntax tree and semantic model 114. In one aspect, the compilation component 112 may be a front-end compiler, a parser, or a language compiler. The syntax tree and the semantic model 114 of each selected source code program is passed to the feature extraction component 116. The feature extraction component 116 extracts certain features of a method invocation from the syntax tree and semantic model. There are several features extracted for each method invocation and these features comprise a feature vector. A portion of the feature vectors generated for a particular class can then be used as training data for the model generation component 112 to train a model 118. Another portion of the feature vectors 120 can be used by the model test component 126 to test the model 120.

Turning to FIG. 7A, there is shown an exemplary source code program 702 from which features are extracted. The source code program 702 contains at line 17 a method invocation of an overloaded method Console. WriteLine with the method signature Console.Writeline(“Hello World”). From this method invocation, features are extracted such as one or more of the following: the position of a method invocation within the program (e.g., span start) 706; whether the method invocation is within a conditional branch (e.g., if-then-else statement, switch or case statement) 708; the class name corresponding to the method invocation 710, the method signature of the method or property invoked 712; the class containing the method 714; the function that contains the called method (containing function) 716; the type of the method 718; and an indication of whether the called method is associated with the static, virtual, override, definition, abstract and/or sealed keywords 720.

Turning back to FIG. 1, the models 128 may then be used in a code completion system. The execution phase 104 may include a source code editor 130 having a user interface 132 and a parser 134, an auto completion component 136, and one or more dictionaries 138. In one or more aspects, code completion may be a function or feature integrated into a source code editor and/or integrated development environment (IDE). Code completion may be embodied as a tool or feature that can be an add-on, plug-in, extension and/or component of a source code editor and/or IDE.

In one aspect, a source code editor 130 may include a user interface 132 and a parser 134. The user interface 132 includes a set of features or functions for writing and editing a source code program. The user interface 132 may utilize a pop-up window to present a list of possible candidates for completion thereby allowing a developer to browse through the candidates and to select one from the list. In this manner, code completion serves as documentation for the method signatures associated with a class in addition to being an assistance to writing code quickly. The parser 134 reads the source code in the source code editor 130 and generates a corresponding syntax tree and semantic model 140. The parser 134 also updates the syntax tree and semantic model 140 as the developer creates and edits the source code in the source code editor 130.

At certain points in the editing process, the user interface 132 will detect that the user has entered a particular character, such as a marker character, that will initiate code completion. In one aspect, a marker character is detected after the name of an entity having one or more accessible members (i.e. contained variables and functions). For example, the marker character may be a period, “.”, placed after a class name. The user interface 132 will then request candidates from the auto completion component 136 to present to the developer.

The auto completion component 136 receives requests 144 for candidates to complete a method invocation. The auto completion component 136 extracts the method signatures of the previous method invocations for the same class in the same document used in the current invocation and the context of the current invocation by accessing the syntax tree and semantic model representation 140 of the source code program in the source code editor 130.

The auto completion component 136 utilizes one or more dictionaries 138 which contain the models 128 in a lookup table format. There is at least one model for each class. A dictionary 138 corresponding to the class name is accessed based on a sequence of the method signatures used in the immediately preceding method invocations. The corresponding entry has a list of method signatures ranked by their predicted probabilities. The auto completion component 136 obtains one or more candidates 142 from the dictionary 138 which are returned back to the user interface 132. In one aspect, at most five candidates are obtained from the dictionary 138. The user interface 132 in turn provides the candidates to the developer. In one aspect, the user interface 132 may provide the candidates from the auto completion component 136 with other candidates from other code completion tools and/or provide the candidates from the machine-learning-based auto completion component separately. The techniques describe herein are not constrained to any particular mechanism for providing the candidates to a developer and the manner in which the candidates are displayed to the user (e.g., pop-up window, etc.).

Turning to FIG. 7B, there is shown exemplary dictionaries based on method signatures. The dictionaries are based on a second-order Markov chain model embodied as a lookup table (i.e., dictionary, key-value pair). In one aspect, there are at least two lookup tables for each class 722A, 722B. One lookup table is for sequences of method signature used in method invocations outside of a conditional branch 722A and the other lookup table is for sequences of method signatures used in method invocations within a conditional branch 722B. The key into either table is a method signature sequence of the two previous method invocations in the System.Console class. The corresponding entry in the table is a list of method signatures in the System.Console class ranked in order of highest probability for completing a current invocation.

As shown in FIG. 7B, when the sequence of preceding method signatures used in method invocations of the System.Console class are Method Signature A followed by Method Signature Y 724, the key into the table is the sequence Method Signature A, Method Signature Y. The corresponding entry in the table 722A lists the code completion candidates as Method Signature B, Method Signature Z, and Method Signature S, ordered in highest probability to lowest probability. Likewise, when the preceding method invocations of the System.Console class are Method Signature J followed by Method Signature A 726, the code completion candidates are Method Signature S, Method Signature U, and Method Signature D. When there is only one preceding method invocation for a class in a document, a null value is used to represent the missing method invocation and the key is the method sequence NULL, Method Signature X 728. The corresponding entry is Method Signature E.

When the current invocation is inside a conditional branch (i.e., if-then-else statement), then the System. Console class conditional branch table 722B is used. The previous sequence of method invocations for the System.Console class in the same document is used as the key into this table. When the preceding sequence of method signatures is Method Signature A followed by Method Signature Y 730, then the code completion candidates are Method Signature NN and Method Signature LN, where Method Signature NN has a higher probability then Method Signature LN. Likewise, when the preceding sequence of method signatures is Method Signature J followed by Method Signature A 732, the code completion candidate is Method Signature ST and Method Signature DY. When there is only one preceding method invocation, the key is the sequence NULL, Method Signature X 734 and the candidate is Method Signature PL.

FIG. 8 illustrates an exemplary method illustrating the generation of the method-signature-based machine learning models for code completion. Referring to FIGS. 1 and 8, one or more source code repositories 106 are searched for source code programs written in a target programming language. The source code repositories 106 can be widely-used code repositories, such as GitHub, internal code repositories, and/or combinations thereof. The source code extraction component 108 extracts a number and type of source code programs that meet an intended target, such as source code programs that are accessed frequently, source code programs that utilize a particular function (e.g., database operations, computer graphics programs, etc.), source code programs having overloaded methods and non-overloaded methods, and the like (collectively, block 802).

The selected source code programs 110 are then compiled by the compilation component 112 to produce data structures representing the syntax tree and semantic model of the source code (block 804). The syntax tree and semantic model 114 are used by the feature extraction component 116 to extract characteristics representative of the context of a method invocation and the method signature used. These characteristics are used to determine the order in which methods are invoked in a program having conditional branches (block 806). The characteristics include one or more of the following: the position of a method invocation within the program (e.g., span start); whether the method invocation is within a conditional branch (e.g., if-then-else statement, switch or case statement); the class name corresponding to the method invocation, the method signature of the method or property invoked; the name of the class that contains the called method; the function that contains the called method; the type of the method; and an indication of whether the called method is associated with the static, virtual, override, definition, abstract and/or sealed keywords.

The characteristics are configured into feature vectors which serve as the training and testing data for the models. In one aspect, the feature vector can be split with 80% used as training data and 20% used as testing data (collectively, block 806).

The feature vectors in the training data are used by the model generation component to generate the models (block 808). The data in the feature vectors is used to determine an order of the method signatures in each program for each class. From the ordered list of method signatures, sequences of usage patterns can be detected. These patterns can then be partitioned into sequences having n+1 states, where n is the order of the Markov chain model. These sequences are then used to train a Markov chain model for each class which entails generating the states and transition probabilities (collectively, block 808).

The training data is analyzed to detect sequences of method invocations for each class. For an n-order Markov chain model, the number of specific n state method invocation sequences that occur is counted to order the n+1 states that occur thereafter by derived probabilities. The derived probability may be generated by the ratio of the number of times the n+1 state sequence occurs over the number of times the n state sequence occurs (block 808).

The models are then tested to ensure a target level of accuracy (block 810). The testing entails providing each model with test data and checking the recommendations that the model outputs. When the recommendations achieve a certain level of accuracy, then the models are transformed into a dictionary or lookup table format and released (block 812).

FIG. 9 illustrates an exemplary method of code completion utilizing the method-signature-based machine learning models. Referring to FIGS. 1 and 9, code completion is performed in a development environment such as a source code editor 130. The source code editor 130 is configured to interact with an auto completion component 136 that utilizes the machine learning models in a lookup table format (block 902). The source code editor 130 performs a background parsing process that parses the source code in the source code editor to generate and update the syntax tree and semantic model of the source code (block 904).

The user interface 132 of the source code editor 130 detects the input characters that a developer enters into the source code editor 130 (block 906). When the user interface 132 detects a particular character that denotes code completion is needed for a method invocation at a current position in the source code editor 130 (block 906), the user interface 132 requests recommendations 144 from the auto completion component 136 (block 908). In one aspect, the detection of a period after a class name is used as the trigger to invoke code completion (block 906).

The auto completion component 138 utilizes the syntax tree and semantic model 140 generated during the source code editing session to obtain the method signatures of the previous method invocations that have occurred before the current position in the source code editor 130 and the characteristics of the context of the current method invocation, such as whether the current method invocation is inside a conditional branch (block 910). In one aspect, application program interfaces (APIs) may be used to extract the method signatures of the previous method invocations from the syntax tree and semantic model and the characteristics of the context of the current position (block 910).

The auto completion component 136 utilizes the dictionary 138 associated with the class to search for a sequence most likely to predict the next method invocation using the characteristics of the context of the current position (block 912). Once the auto completion component 136 obtains the method signatures of the previous method invocations, an n-state sequence can be constructed and used as a key to access the dictionary. The corresponding values are used as the recommendations. If there is no such n-state method signature sequence, then the dictionary is searched using an n−1 state method signature sequence constructed from the method signatures of the previous n−1 method invocations in the same class. If the n−1 state method signature sequence cannot be found in the dictionary, then the n−2 state method signature sequence is used to search the dictionary. In an n-order Markov chain model, the n−1 state method signature sequence will be stored as a new n state method signature sequence with the first state marked as null.

The auto completion component 136 may find one or more candidates for recommendation from the sequences in the dictionary (block 912). In the event that there are multiple candidates, the auto completion component 136 orders or ranks the recommendations by highest probability (block 914). The candidates are then returned to the user interface for display to the developer (block 916). In addition to the candidates, additional information may be provided to the user about the recommendations for the user (block 916). The user may select one of the recommendations or choose to ignore the recommendations. In the event the user selects one of the recommendations (block 918), the user interface accepts the selected recommendation which is then inserted into the source code program (block 918).

FIG. 10 illustrates an exemplary user interface 1000 which includes an exemplary source code program (lines 12-26) in a source code editor that displays pop-up window 1002 containing candidates for code completion and another pop-up window 1004 that contains a description of the most likely candidate. As shown in FIG. 10, the suggested method to complete the expression Directory is the method signature CreateDirectory(string path). FIG. 10 displays pop-up window 1002 containing multiple recommendations such as Delete, CreateDirectory, Exists, and GetFiles. The recommendations from the auto completion component may be distinguished with a star * and other recommendations may be included thereafter in alphabetical order (not shown). In this example, the auto completion component uses the second order Markov model sequence NULL, Directory.Exists(String) to find the most likely candidate to recommend for this particular method invocation.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

A system is described that includes at least one processor and a memory. The memory includes at least one module that provides code completion information to a user of a source code editor. The at least one module includes instructions that when executed on the at least one processor performs actions that: detect that code completion information is to be obtained to complete a method signature of an invocation of an overloaded method; obtain the code completion information from a machine learning model using at least one sequence of method signatures of method invocations immediately preceding the detected overloaded method invocation; and insert the code completion information into the source code program.

The at least one module includes further instructions that when executed on the at least one processor performs actions that: generate a syntactic representation and a semantic representation of the source code program; and use the syntactic representation and the semantic representation to obtain the at least one sequence of method signatures of the method invocations immediately preceding the detected overloaded method invocation. The method invocations immediately preceding the detected overloaded method invocation and the detected overloaded method invocation are from a same class. The machine learning model is a n-order Markov model and the n-order Markov model includes sequences of method signatures and a transitional probability that a n+1 method signature is likely to follow the immediately preceding sequence of n method signatures. The method signature contains zero or more parameters.

A device is disclosed comprising one or more processors and a memory. One or more programs are stored in memory and configured to be executed by the one or more processors, the one or more programs including instructions for: tracking an ordered sequence of method signatures used in one or more method invocations in a source code program; detecting a marker character; obtaining one or more candidates to complete a method signature of a method invocation following the marker character, the one or more candidates associated with a probability of following the marker character based on the tracked ordered sequence of method signatures preceding the marker character; and inserting at least one of the one or more candidates to complete the method invocation in the source code program.

The one or more candidates are from a class associated with the method invocation. The probability of the one or more candidates following the marker character is based on a context of the marker character in the source code program. Obtaining the one or more candidates to complete the method invocation following the marker character further comprises: obtaining a n-order Markov model for a class associated with the method invocation, the n-order Markov model accessed by n method signatures preceding the marker character; and using the n-order Markov model to obtain the one or more candidates.

Obtaining the one or more candidates to complete the method invocation following the marker character further comprises: obtaining a n-order Markov model for a class associated with the method invocation, the n-order Markov model accessed by n−1 method signatures preceding the marker character when n preceding method signatures from a same class as the method invocation do not exist in the source code program; and using the n-order Markov model to obtain the one or more candidates. The marker character is preceded by a class name. The method signature does not include a parameter.

A method is disclosed that can be embodied on the system and device described herein comprising: obtaining at least one method signature of a previous method invocation in a source code program preceding a current method invocation in a source code editor, wherein the at least one method signature of the method invocation and the current method invocation are of a same class; utilizing a Markov chain model associated with the same class to predict one or more recommendations of method signatures to complete the current method invocation based on the at least one previous method signature, wherein the Markov chain model includes one or more sequences of method signatures of method invocations, a sequence including transition probabilities representing a likelihood of transitioning from one method invocation having a first method signature to another method invocation in a sequence having a second method signature; obtaining at least one of the one or more predicted recommendations of method signatures from the Markov chain model using the at least one method signature of a previous method invocation; and completing the method invocation using at least one of the recommended method signatures.

The method further comprises ranking the one or more recommended method signatures based on a probability associated with the recommended method signatures. The method further comprises providing a description of a recommended method signature along with a ranked list of the one or more recommended method signatures and prior to obtaining the at least one method signature of the overloaded method, detecting a marker character after a class name.

The method further comprises generating the machine learning model as a n-state Markov chain model having sequences of n method signatures that occur prior to an n+1 state. A sequence includes transition probabilities of a likelihood of transitioning from one method signature to another method signature in the sequence. The probability is derived from sampling usage patterns of overloaded methods in a sampled populations of source code programs. 

What is claimed:
 1. A system comprising: at least one processor and a memory; wherein the memory includes at least one module that provides code completion information to a user of a source code editor, the at least one module including instructions that when executed on the at least one processor performs actions that: generate a syntactic representation of a source code program; detect that code completion information is to be obtained to complete a method signature of an invocation of an overloaded method of the source code program; use the syntactic representation to obtain at least one sequence of method signatures of the method invocations immediately preceding the detected overloaded method invocation; obtain the code completion information from a sequential machine learning model using the at least one sequence of method signatures of method invocations immediately preceding the detected overloaded method invocation, the at least one sequence of method signatures of method invocations of a same class as the detected overloaded method invocation; and insert the code completion information into the source code editor.
 2. The system of claim 1, wherein the at least one module includes further instructions that when executed on the at least one processor performs actions that: generate a semantic representation of a source code program; and use the syntactic representation and the semantic representation to obtain the at least one sequence of method signatures of the method invocations immediately preceding the detected overloaded method invocation.
 3. The system of claim 1, wherein the method invocations immediately preceding the detected overloaded method invocation and the detected overloaded method invocation are invoked within a same method.
 4. The system of claim 1, wherein the sequential machine learning model is a n-order Markov model.
 5. The system of claim 4, wherein the n-order Markov model includes sequences of method signatures and a transitional probability that a n+1 method signature is likely to follow the immediately preceding sequence of n method signatures.
 6. The system of claim 5, wherein the method signature contains zero or more parameters.
 7. A device comprising: one or more processors; and a memory; one or more programs, wherein the one or more programs are stored in memory and configured to be executed by the one or more processors, the one or more programs including instructions that perform acts for: tracking an ordered sequence of method signatures used in one or more method invocations in a source code program; detecting a marker character; obtaining one or more candidates to complete a method signature of an invocation of an overloaded method, following the marker character, from a sequential machine learning model, the one or more candidates associated with a probability of following the marker character based on the tracked ordered sequence of method signatures preceding the marker character from a same class as the overloaded method, wherein the probability of the one or more candidates following the marker character is based on a context of the marker character in the source code program; and inserting at least one of the one or more candidates to complete the method invocation in the source code program.
 8. The device of claim 7, wherein the tracked ordered sequence of method signatures are located within a same method as the marker character.
 9. The device of claim 7, wherein the one or more programs including instructions to perform acts for: obtaining a n-order Markov model for a class associated with the method invocation, the n-order Markov model accessed by n method signatures preceding the marker character; and using the n-order Markov model to obtain the one or more candidates.
 10. The device of claim 7, wherein the one or more programs including instructions to perform acts for: obtaining a n-order Markov model for a class associated with the method invocation, the n-order Markov model accessed by n−1 method signatures preceding the marker character when n preceding method signatures from a same class as the method invocation do not exist in the source code program; and using the n-order Markov model to obtain the one or more candidates.
 11. The device of claim 7, wherein the marker character is preceded by a class name.
 12. The device of claim 7, wherein the method signature does not include a parameter.
 13. A computer-implemented method, comprising: tracking a sequence of method signatures used in method invocations in a method of a source code program; detecting an incomplete method signature of an overloaded method invocation; using an n-order sequential machine learning model to find candidate method signatures that match a sequence of method signatures of method invocations of a same class as the incomplete method signature, wherein the sequence of method signatures of method invocations is located in a same method as the incomplete method signature, wherein the sequence of method signatures of method invocations immediately precedes the incomplete method signature; upon finding a match, obtaining a candidate method signature to complete the incomplete method signature using the n-order sequential machine learning model; and providing the candidate method signature to the source code program.
 14. The method of claim 13, further comprising: obtaining an n-state sequential machine learning model for the same class; and obtaining an n-state sequence of method signatures of method invocations preceding the incomplete method signature.
 15. The method of claim 14, wherein the n-order sequential machine learning model is an n-order Markov model.
 16. The method of claim 14, wherein the n-order sequential machine learning model includes a transitional probability that a n+1 method signature is likely to follow the sequence of n method signatures.
 17. The method of claim 13, further comprising: upon not finding a match, using an n−1 state sequence of method signatures of method invocations preceding the incomplete method signature; and using the n−1 state sequence of method signatures to obtain a candidate method signature from the n-order sequential machine learning model. 